Trunking communication systems are known to comprise a plurality of communication units, a limited number of communication resources that are transceived via a predetermined number of repeaters, or base stations, and a communication resource allocator that allocates a limited number of communication resources among the plurality of communication units. The communication resources may comprise a TDM bus, a carrier frequency, a pair of carrier frequencies, or any RF transmission means. Of the communication resources, one is selected as the control channel to transceive operational data between the communication resource allocator and the communication units. The communication units, which may be portable radios and/or mobile radios, are arranged into talk groups by commonality of use. For example, a talk group may comprise communications that are operated by a police department while another talk group comprises communication units operated by a fire department.
In the thinking communication system, a communication unit initiates a communication for its talk group by transmitting a request to the communication resource allocator. The request typically contains the communication units individual identification code and its talk group identification code. If the communication resource allocator grants the request, a communication resource is allocated to that particular talk group. Typically, the requesting communication unit begins the communication by transmitting voice data. When another member within the talk group wishes to transmit its own voice data, it activates a request to transmit, which is typically done by activating a push-to-talk button. If the requesting communication unit is still communicating when another communication unit transmits a request to communicate, the subsequent requesting communication unit will not receive the remaining communication from the requesting communication unit. This results because the communication resource allocator does not respond to the subsequent request to communicate until the preceding request to communicate has been completed, i.e. the requesting communication unit has finished transmitting its voice data. Therefore, a need exists for a method that allows a communication unit to receive any remaining of communications from another communication unit after it has initiated a request to communicate.